Vulcanization of butyl rubber with 2, 6-dimethylol-3, 5-dimethyl-4-chlorophenol, andvulcanizate obtained thereby



United States Pa 2,987,497 VULCANIZATION F BUTYL RUBBER WITH 2,6- DlME'IHYLOL3,5-DIMETHYL 4 CHLOROPHE- NOL, AND VULCANIZATE OBTAINED THEREBY Richard Leshin, Akron, Ohio, assignor to The Goodyear The beneficial vulcanizing action discovered for 2,6-

Tire R 1 of ubber Company Akron a comma d1methylol-3,5-d1methy1-4-chlorophenol on Butyl rubber N D i Fil D 24, 195 s 732,629 is most unexpected because, even though S. Van der Meer 4 Claims. (Cl. 260-43) teaches in Mededeelingen van Het Kunststoffeninstituut This invention relates to a method of vulcanizing Butyl 10 Rubber'sfitching Delft: 41, in an article rubber and the vulcanizate bt i d h b entitled The Vulcanization of Rubber With Phenol Form- It is known that rubbery polymers, both natural and aldehyde Derivatives, on p 4 thereof t synthetlc, may be converted from a crude stock into a methylol-4-chlorophenol and 2,6-dimethylol-3-methyl-4- stock through a PromsS known as f chlorophenol will bring about the vulcanization of natural 3 5: :5 any Of a grfeat g g f vulcamzmg 15 rubber and synthetic rubbers of the diene type, the use g mos common 0 W 18 SH of of these two compounds in Butyl rubber produces an inimany man-made rubbers developed 1n recent years, parti a1 1 ti f B t 1 bb th t d t t b (H ticularly those based on the use of a conjugated diene, one vu 9 u y er a e enora es y of the most difficult to convert from a crude stock into a upon agmg' Information would leafl one to vulcanized stock having excellent heat and age resistance 20 that the next hlgher homologue 3 is the rubbery copolymer known i th trade as B l methyl-4-chlorophenol, would also behave in a similar rubber, which is made by polymerizing a mixture of a manner. However, it was discovered that when Butyl ma or proportion (9099.5% and preferably about 95- rubber is cured with 2,6-din1ethylol-3,5-dimethyl-4-chloro- 99 .5%) f a r-C7 1800161111, 115113113 lsoblltylene, and a phenol physical properties are developed which are sug g g i alldlPeferablylabPut 5 to perior to those developed by the next lower homologue a) a 4 conjugate (110.6 usual y lsoprene and most important these physical properties are not serior butad1ene-1,3, in accordance with well known techousl afie t d b It 0 t t t d niques as described, for example, in United States Patent y c e y 1 S lmpor an an Essen" 2,356,128. For purposes of convenience, this class of Hal that Butyl mPber not detenorate P copolymers 111 be designated by the general term putyl 3 ample, when sub ected to steam and air, especially when rubber. the Butyl rubber is to be used in the construction of curing It has now been discovered that Butyl rubber may be elements, pressure hose, conveyor belts, and Bag-O-Matic converted to a more heat and age resistant condition, and bl dd f use i Bagelvj fi i presses as h therefore 3 usFful Product by heatmg the Butyl example, in Machinery and Equipment for Rubber and rubber vulcamzatlon temperature zfi z of Plastics 1 314-19 (1952), and for other uses as shown, the speclfic coinpound 26'd1methylo1'3 'dlme y 'chlofor example in United States Patent 2,857,357. rophenol havmg the formula R The following examples show the efiect of 2,6-dimethylol-3,5-dimethyl-4-chlorophenol and the next lower KOCH CHOH 40 homologues on curing Butyl rubber stock and how the CH CH properties of the cured stock are affected by aging for a twelve hours in an autoclave charged with air and wet I steam. All parts are by weight unless otherwise indicated.

Example 1 Example 2 Example 3 Example 4 15141111 112 0 Butyl Rnbbei 9(acom netiJ-cltal grade 01 7a iiiiia r i fiiufil fif y m an 3. 100.00 100.00 100.00 100.00 100.00 Carbon Black 50. D0 50. 00 50.00 50.00 50.00 Stearic Acid (Processing Aid) 1. 1. 50 1. 50 1. 50 1. 50 2,6-Dimethylol-4-Ohlorophenol 12.00 2,6-Dimethylo1-3-Methyl-4-Ch1orophenol 12. 00 6. 00 2,6 Dimethylol 3,5 Dimethyl 4 Chloro nl'mnnl 12.00 6.00 stzifiauiglgorlde Drhydrate (SnCl1.2H 0) 2' 00 v 2 00 Orig. Aged Orig. Aged Orig. Aged Orig Aged Orig Aged fifi l f 940 1, 620 9 0 1,980

1,430 1, 320 1, 320 1,900 2, 230 1,220 1,170 2,510 2,570 TB 1, 550 1, 340 2,080 TS 1, 350 1,280 2,610 2,640

TS-Too short to measure.

observed that 2,6-dimethylol-4@chlorophenol develops considerably less tensile strength at 300% modulus than does 2,6-dimethylol-3-methyl-4-chlorophenol which in turn develops less tensile than does the compound of this invention when cured for 35 minutes at 330 F. A correspondingly substantial improvement is also observed when the compound of this invention is used in combination with an activator such as stannous chloride over the next lower homologue when used with the same activator. The same general improvement is also observed with respect to the tensile strength developed at ultimate elongation. Most important, however, is the improvement in percent set which is developed by the compound of this invention over the next two lower homologues. The same general improvement is also to be observed when the compound of this invention is used in combination with stannous chloride in regard to compression set and taken in comparison with the next lower homologue, as shown in Example 3.

The curing agent of this invention useful in the cure of Butyl rubber may be used in amounts of from 1.0 part to 250 parts per 100 parts of rubber. It is preferred to use from 6.0 to 12.0 parts.

Although the next lower homologue of the curing agent of this invention cures Butyl rubber when used in combination with a vulcanization accelerator, the resulting cured Butyl rubber does not have as desirable physical properties as does Butyl rubber when cured with 2,6-dimethylol-3,5-dimethyl-4-chlorophenol used either without a vulcanization accelerator as shown in Example 4 or with a vulcanization accelerator as shown in Example 5. The resulting cured Butyl composition made in accordance with the foregoing examples possesses better hot elongation properties, better resistance to crack growth, greater resistance to tear, and has a lesser modulus increase than when Butyl rubber is cured with other types of phenol dialcohois, as for example polymers of 2,6-dimethylol-4-hydrocarbon substituted phenol and polymers of 2,6-dimethylol-3,4,5-hydrocarbon substituted phenol. The cured Butyl stock of this invention may be used under more severe conditions of heat and stress than when Butyl stock is cured with other known curing agents. Additionally, the curing agent of this invention produces efiicient and economical cures of Butyl rubber without the use of a vulcanization accelerator. curing agent of this invention may be used in its naturally recovered state, which is a fine crystalline material. Other phenol dialco'hols particularly of a resinous nature must be ground to a very fine state before they may be used as curing agents for Butyl rubber since they are not otherwise readily dispersed in the Butyl rubber being cured as is the case of the vulcanization accelerator of this invention. a I a 7 Should it be desired to use a vulcanization accelerator Additionally, the

in combination with 2,6-dimethylol-3,5-dimethyl-4-chlorophenol, chlorinated compounds are particularly useful chloride, chromium chloride, nickel chloride, cobalt chloride, manganese chloride, and copper chloride.

Butyl rubber cured in this manner may also becompounded in any well known and conventional manner using plasticizers such as mineral oil, carbon black, zinc oxide, stearic acid, zinc stearate, and other well known 4 compounding ingredients to bring about the desired etfects in the vulcanized state. jl'he Butyl rubber may be compounded in a conventional way using rubber mixing equipment such as an internal mixer or roll mills.

The resulting compounded Butyl rubber may be fabricated into any desired form by the usual methods such as calendering, extrusion, or molding, and is admirably adapted in the manufacture of such articles as curing elements useful under extreme conditions of heat and pressure, as for example useful in the manufacture of a curing bag which is used in shaping a pneumatic tire within a mold. It is observed that curing elements of this nature have a greater useful life than when made from Butyl rubber treated with conventional curing compounds, such as the quinone-dioxime type of cure as described in Industrial and Engineering Chemistry 40, 2314- 19 (1948); U.S. 2,393,321 (1946); and in a technical bulletin by the Enjay Company entitled Butyl 1948.

The curing process of the invention is conventionally carried out at temperatures of 200 F. up to 400 F. for periods of time ranging from about five minutes to about three hours and preferably within a vulcanizing temperature range of about 300 to 350 F.

The Butyl rubber used in the examples above was made by reacting 96 parts by weight of isobutylene with 4 parts by weight of isoprene dissolved in methyl chloride and then polymerized at -'-100 C. in the presence of 0.2 part by weight of aluminum chloride. The resulting copolymer contained 98% by weight of isobutylene and 2% by weight of isoprene.

While certain representative embodiments and details have been shown for the purpose of illustrating the in-- vention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the in-- vention.

What is claimed is:

1. An elastic vulcanizate comprising a rubbery copolyrner of an isoolefin having from 4 to 7 carbon atoms with from 0.5 to 10% of a conjugated diolefin having from 4 to 8 carbon atoms, vulcanized with from 1 to 25 parts of 2,6-dimethylol-3,5-dimethyl-4-chlorophenol per 100 parts of the rubbery copolymer.

2. The vulcanizate of claim 1 in which an accelerator of vulcanization is present during the vulcanization.

3. The vulcanizate of claim 2 in which the accelerator is stannous chloride.

4. A method of vulcanizing Butyl rubber which comprises the steps of mixing a rubbery copolymer of an isoolefin having from 4 to 7 carbon atoms with from 0.5 to 10% of a conjugated diolefin having from 4 to 8 carbon atoms with 2,6-dimethylol-3,5-dimethyl-4-chlorophenol, shaping the said mixture and thereafter heating the said mixture at a temperature of from 200' F. to 400 until the mixture is converted to an elastic vulcanized state.

References Cited in the file of this patent UNITED STATES PATENTS Pays-Bas, volume 63, No. 40 (1944), pages 147-169, page 150 relied upon. 

1. AN ELASTIC VULCANIZATE COMPRISING A RUBBERY COPOLYMER OF AN ISOOLEFIN HAVING FROM 4 TO 7 CARBON ATOMS WITH FROM 0.5 TO 10% OF A CONJUGATED DIOLEFIN HAVING FROM 4 TO 8 CARBON ATOMS, VULCANIZED WITH FROM 1 TO 25 PARTS OF 2,6-DIMETHYLOL-3,5-DIMETHYL-4-CHLOROPHENOL PER 100 PARTS OF THE RUBBERY COPOLYMER. 